The present application relates to data storage devices, and particularly to suspensions used in microactuators for sliders in data storage devices.
Many data storage devices are used in computer equipment which include a moving medium such as a disc upon which information is stored in concentric tracks. A head is traversed over the surface of the disc to read information from the disc and/or write information to the disc. For instance, the disc can be a magnetic disc or an optical disc.
In many high density storage devices, the head is mounted on a slider. The slider includes an air bearing surface which opposes the disc surface. As the disc rotates, the disc drags the air in a xe2x80x9cwindxe2x80x9d under the slider along the air bearing surface in a direction approximately parallel to the tangential velocity of the disc. The air incident on the air bearing surface creates a lifting force that causes the slider to lift and fly in immediate proximity over the disc surface. The magnitude of the hydro-dynamic lifting force depends on the air bearing properties of the slider and the speed of rotation of the disc. A preload force is supplied to the slider to counteract the hydro-dynamic lifting force. The magnitude of the preload force is designed to be in equilibrium against the lifting force at a desired flying height, positioning the slider as close as reliably possible to the moving disc surface.
The slider is typically supported on a load beam which provides the preload on the slider toward the disc. The load beam is in turn supported on an actuator arm which is moved relative to the disc surface, such as by a voice coil motor. The load beam at its distal end includes a gimbal which allows the slider to pitch and roll about a gimbal point relative to the surface of the disc.
There is a continual desire with data storage devices to decrease size, increase storage density, and reduce cost. To decrease size and increase storage density, tracks on the disc at which data is stored are positioned closer and closer together. Higher track densities make positioning of the head more important for accurate reading and writing of data. As track density increases, it becomes increasingly difficult for the voice coil motor and servo control system to quickly and accurately center the head over the desired track.
As precise positioning of the head becomes more critical, it also becomes more difficult to accurately position the head with a single actuation source. Accordingly, microactuators have been proposed to further position the head relative to the disc. The microactuator provides fine position control, while the large actuator arm provides macro position control so the head can transverse over the entire surface of the disc.
Microactuators have been proposed in several locations: between the actuator arm and the load beam, between the load beam and the slider, and between the slider and the transducer or optical element. For microactuators placed between the slider and the transducer or optical element, a tiny size is critical so as to not interfere with the flying characteristics of the slider. For other locations of microactuator placement, strength of the microactuator suspension is important, because the microactuator suspension must transmit forces between the slider and the actuator arm as well as provide fine position control. The present invention particularly relates to such microactuator suspensions which transmit forces between the actuator arm and the slider.
Microactuator suspensions include two pads connected by a flexible, resilient support element to allow movement of the two pads relative to each other. A motive element is included which provides the force for movement of the two pads relative to each other. For instance, the motive element can be an electromagnet, with a stator positioned on one of the pads and a magnetically responsive element positioned on the other of the pads. Various other types of motive elements, including electrostatic, piezoelectric elements, etc. can alternatively be used to move one pad relative to the other for fine position control.
A microactuator suspension assembly includes a microactuator suspension supporting a slider. The microactuator suspension has at least a first resilient support extending from a slider attachment pad to a suspension arm attachment pad. In one aspect, the slider attachment pad contacts the slider on a side face of the slider, and the microactuator adds little or nothing to the vertical thickness of the head gimbal assembly. In another aspect, the suspension arm attachment pad attaches to the gimbal with an attachment bridge which is longitudinally balanced relative to the gimbal point and air bearing centroid of the slider, and moments and localized stresses on the resilient support are minimized.
A benefit of the microactuator suspension is that it acts a mechanical low pass filter attenuating vibrations experienced by the slider. Specifically, the resilient supports comprise one or more beams which support the slider. These beams act as a simple spring mass system having a single resonant frequency, followed by attenuation or xe2x80x9crolloffxe2x80x9d. The rolloff after the microactuator resonance tends to reduce the effect of vibrations caused by the windage experienced by the microactuator as it flies above the rotating disc.